To serve immediately:
a) Stovetop: Heat oil in a small skillet on medium-high heat. With the entire block of tempeh intact, sear each side for 3 minutes.
b) Air fryer: Spritz each side of the tempeh with canola or olive oil. Cook in an air fryer on 390°F for 5 minutes, shaking halfway.
Slice and serve.
To store: Place bag in ice water before storing in the refrigerator (up to 3 days) or freezer (up to 1 month).